1. Field of the Invention
The invention relates in general to a method of identifying a type of an optical disc, and more particularly to a method of identifying a Digital Video Disc-Random Access Memory (DVD-RAM).
2. Description of the Related Art
Nowadays, Digital Video Discs (DVDs) are categorized into Read Only Memory DVD (DVD-ROM), write-once DVDs (DVD+R or DVD−R), Rewriteable DVDs (DVD+RW or DVD−RW) and DVD-RAM. Among all types of DVDs, the specification of DVD-RAM is the most complicated. FIG. 1 shows the outline of the DVD-RAM disc. The DVD-RAM disc 100 is divided into an embossed area 120 and a rewriteable area 110. The embossed area 120 is located in the inner tracks of the DVD-RAM disc for providing the information of the disc such as the storage capacity or the type of the disc. There is no embossed area in other types of DVDs. Moreover, the most distinguishable feature of the DVD-RAM disc is that the DVD-RAM disc has a number of headers 130 in the rewriteable area. The physical addresses of data are stored in the header such that data can be written in or deleted from the DVD-RAM disc anytime like a hard disk.
The optical drives in the current market typically support every DVD standard. Whenever an optical disc is placed in, the optical drive determines the type of the disc firstly. The following steps determine whether the disc is a DVD-RAM disc. After the optical disc in the optical drive begins to spin, the optical drive calculates the amount of headers per track 140. If the calculated amount of the headers is larger than a predetermined amount, the optical disc is identified as a DVD-RAM. However, if the optical disc in the optical drive is not a DVD−RAM disc but a DVD+RW disc or a DVD−RW disc, the noise in the detected signal when reading the empty tracks may be mistook for headers by the optical drive. It may further result in the optical drive inaccessible to the optical disc.
Therefore, how to determine whether the optical disc is DVD-RAM or not correctly and efficiently is an important issue for the optical drive to access the optical disc properly.